This invention relates to flame retardant compositions containing at least one tetrahalophthalate ester and a polyphenylene ether resin. This invention also comprehends the method of improving the flame retardancy and processability of the polyphenylene ether resins by using these tetrahalophthalate esters.
Polyphenylene ether resins are known in the art as a class of thermoplastics which are characterized by excellent physical properties, including hydrolytic stability, dimensional stability and excellent dielectric properties. In general, they are prepared by the oxidative coupling of a phenolic compound with complex metal catalysts, e.g., a complex copper catalyst. The preparation of polyphenylene ether resins is described in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875 and U.S. Pat. Nos. 3,257,357 and 3,257,358 of Stamatoff, the teachings of which are incorporated herein by reference.
The high molecular weight polyphenylene ethers are high performance engineering thermoplastics possessing relatively high melt viscosities and softening points, that is, in excess of 250.degree. C., and are useful for many commercial applications requiring high temperature resistance including formation of film, fiber, and molded articles.
Cisek, U.S. Pat. No. 3,383,435, which is incorporated herein by reference, discloses polyphenylene ether-styrene resin compositions including rubber-modified styrene resin-polyphenylene ether resins wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. Although the styrene resin component improves the moldability of the polyphenylene ethers these compositions are still difficult to process.
Polyphenylene ether/styrene resin blends comprising between about 25 and 75% of polystyrene units are available commercially from the General Electric Company under the NORYL.RTM. trademark.
The use of brominated and/or chlorinated compounds by themselves or in combination with other materials such as organic phosphates, boron compounds, etc., as flame retardants for polyphenylene ether resin compositions are well known in the art and are exemplified by U.S. Pat. Nos. 3,257,357; 3,639,506; 3,733,307; 3,809,729; 3,867,336; 3,919,356; 3,936,414; 3,974,235; 3,939,531; 4,024,093; 4,034,136 4,073,772; 4,094,856; 4,096,117; 4,107,232; 4,191,685; 4,203,931; 4,206,154; 4,274,998; 4,280,951; 4,298,514; 4,301,062; 4,355,126; 4,403,057; 4,446,272; and 4,456,720. The aforesaid patents are incorporated herein by reference.
Tetrahalophthalate esters have been used as flame-proofing materials. For example, U.S. Pat. No. 4,098,704 describes the use of these materials as textile finishing agents. U.S. Pat. Nos. 4,298,517 and 4,397,977 disclose these compounds as flame retardants for halogenated resins. However, no teachings have been found which show the use of these compounds as flame retardants or processing aids for polyphenylene ether resins.